Effective Viscosity and Glass Transition Temperature of Cs₂O–B₂O₃ Melts

Abstract—The effective viscosity (viscoelasticity) of cesium–borate melts has been measured in the temperature interval 900–1600 K at Cs₂O concentration x varying from 0 to 16 mol % by the method of vibrational viscometry. It has been shown than vibration causes a non-Newtonian flow of melts. This means that the activation energy of viscous flow is related not only to the configuration activation energy (the switching energy of oxygen bridge bonds) but also to the elastic energy of structural units in the melt. Using the parameters of Newtonian and non-Newtonian flows, shear viscosity η', elasticity modulus G ', and storage viscosity η" have been calculated. It has been found that in the case of high shear rates, cesium–borate melts may be considered as fluids with viscous and elastic properties. Glass transition temperature T_g has been determined by the differential scanning calorimetry method, and its dependence on cesium oxide concentration has been explained.